This invention relates to microwave devices such as frequency multipliers, of the type wherein a semiconductor varactor diode is driven by microwave power at one frequency to produce microwave power at another, harmonically related frequency.
Prior art devices generally consist of a resonant enclosure containing the varactor and provided with suitable input and output ports, impedance matching and tuning means. The enclosure frequently consists of a length of waveguide proportioned to operate in the dominant TE.sub.10 mode at the frequencies involved. Such expedients as reduced-height waveguide sections are commonly required to facilitate matching the relatively low impedance of the varactor diode.
As the micorwave spectrum in use extends further into the millimeter wave region, the prior art structures become smaller and more difficult and expensive to fabricate. Also, because presently available millimeter wave sources are of relatively low power capability, minimization of circuit losses is important. A further and more basic power limitation is imposed by the fact that the varactor must be almost microscopically small to operate at such frequencies, with correspondingly low power handling capability.